Chapter 3: Understanding the Brain and Brain Injury

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Chapter 3 Understanding the Brain and Brain
Injury
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Module Objectives

• Identify basic brain structures and functions.
• Describe brain-behavior relationships.
• Describe how an injury to the brain can result in
  various behaviors and challenges.

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Introduction

• The brain is the main organ of learning.
• It makes it possible for us to think,
  communicate, act, behave, move about, and create.
  

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Mechanisms of Traumatic Brain Injury

• After a sudden jolt or bang, the result can be
• Coup-Contracoup Injury at the site of impact and
  on the opposite side from the movement of the
  brain against the skull (either front to back or
  side to side)

Courtesy Centre for Neuro Skills
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Mechanisms of Traumatic Brain Injury

• After a sudden jolt or bang, the result can be
• Diffuse Axonal injuries Delicate nerve tissues
  rip, tear, and stretch
• Swelling Brain tissue swells preventing blood
  and CSF circulation

• Hematoma Accumulation of blood causing pressure
• Hydrocephalus Blockage of CSF causing pressure
• Anoxia Hypoxia Oxygen deprivation from
  suffocation, drowning, blood loss, or cardiac
  failure that kills brain cells

Courtesy Centre for Neuro Skills

• Hemorrhages Major bleeding from when the brain
  rubs against the inside of the skull, which is
  ragged with sharp bony ridges

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When the Brain is Injured

• A brain injury is often the result of two
  injuries
• A primary injury caused by the initial blow or
  insult to the brain
• A secondary injury caused by the swelling,
  bleeding, compression and contusions (bruises) to
  the brain.

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Severity of Brain Injuries

• Glasgow Coma Score (GSC)
• Is a measure of brain injury severity.
• Measures Eye Response Verbal Response Motor
  Response Total Score
• Scores range between 3 and 15
• The lower the score, the more severe the brain
  injury

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Severity of Brain Injuries
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Severity of Brain Injuries

• Post concussion symptoms of cognitive and
  psychiatric nature that may or may not persist
  include
• headache changes in personality
• dizziness memory problems
• vomiting depression
• sleep disturbance difficulty problem solving
• irritability diminished attention span

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Anatomy of the Brain

• The brain . . .
• Is a soft organ, like the consistency of gelatin
• Weighs less than 1 lb. at birth and grows to
  about 3 lbs.
• Sits inside a rough and bony skull and is bathed
  in a cerebrospinal fluid (CSF)
• Receives oxygen and glucose through a
  sophisticated system of blood vessels that carry
  blood to and from the heart

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Anatomy of the Brain

• Three membranes or meninges cover the brain

• The outer dura mater or hard matter, which is
  like a heavy plastic covering.
• The arachnoid, which is like a spider web that
  bridges the brain's many wrinkles and folds.
• The pia mater or tender matter, which molds
  around every tiny crook and crevice on the
  brain's surface.
• Between the pia mater and the arachnoid, there is
  145cc of cerebrospinal fluid.

Scalp
Skull
Dura Mater
Arachnoid
Pia Mater
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Anatomy of the Brain

• There are four ventricles which make, store, and
  circulate cerebrospinal fluid.
• The fluid helps cushion the brain and protect
  brain tissue when swelling occurs.

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Neurons

• Neurons the billions and billions of tiny brain
  cells making up the nervous system
• Glial ("glue") non-communicating cells support
  and nourish the neurons.
• Three main parts of the neuron

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Neurons

• The neurons communicate with each other via a
  unique electro-chemical process.
• Neurotransmitters are chemical messengers that
  relay the electrical signal of one nerve cell to
  the next.
• Neurochemical transmitters leap the synaptic
  gaps.
• After a person sustains a brain injury, many of
  the neuron pathways may be torn apart or
  stretched so that information processing is no
  longer possible.

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Brain Stem

• Midbrain
• Alertness arousal
• Elementary forms of seeing hearing
• Pons
• Facial movement sensation, hearing,
  coordinating eye movements
• Medulla
• Basic living functions
• Vital to life and death
• Controls involuntary functions like breathing,
  heart-rate, blood pressure, swallowing, vomiting
  and sneezing.

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diencephalon

• Thalamus
• Major relay station for incoming and outgoing
  sensory information
• The input for every sense (except smell) travels
  through the thalamus
• Hypothalamus
• Control center for hunger, thirst, sexual
  response, endocrine level temperature
  regulation.
• Controls complex responses like anger, fatigue,
  memory and calmness.

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Limbic System

• Limbic System
• Houses basic elemental drives, emotions and
  survival instincts.
• Injury to the limbic system can result in serious
  problems with basic emotional perceptions,
  feelings responses.
• Behavior and mood can be very erratic

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Limbic System

• Amygdala
• Fight or flight structure
• The front door to our emotions
• When perceptions reach the cerebral cortex, it is
  transmitted to the amygdala to be evaluated for
  emotional content

• Hippocampus
• Associated with memory functions
• Injury can result in problems with short term
  memory, and turning short term memories into long
  term memories
• Disrupts the encoding and retrieval of long term
  memory

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The Cerebral Cortex

• Cerebral Cortex the most complicated structural
  component of the brain
• Made up of two hemispheres the right hemisphere
  and left hemisphere
• Dedicated to the highest levels of thinking,
  moving, and acting.
• Each hemisphere is divided into four lobes
  frontal, parietal, temporal, and occipital
• The cortex is full of wrinkles and folds.
• If you took out and flattened the cortex, it
  would be the size of a pillowcase.

Right Hemisphere
Left Hemisphere
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The Cerebral Cortex

• The two hemispheres of the brain have unique ways
  of processing information.
• The right hemisphere is more holistic,
  visualspatial, and intuitive.
• The left hemisphere processes language and is
  more linear, verbalanalytic, and logical.
• The cerebral hemispheres control opposites sides
  of the body.
• The cerebral hemispheres communicate to each
  other a thousand times a second through the
  corpus collosum (the 4 inch long, pencil thick
  band of complex nerve fibers).

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Lateralized Skills of the Brain

• The brain is divided into two hemispheres
• The left hemisphere controls the right side of
  the body.
• The right hemisphere controls the left side of
  the body
• The two hemispheres control input and regulate
  output

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Lobes of the Brain
Parietal lobe
Frontal lobe
Occipital lobe
Temporal lobe
Cerebellum
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Lobes of the Brain continued

• The lobes are interconnected by complex neural
  fibers, which relay impulses and information to
  and from the cortex.
• Each lobe has a right and left side.

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Brain Behavior Relationships

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Frontal Lobes

• Prefrontal cortex located at the very front part
  of the frontal lobes
• Helps hold information in memory for several
  minutes (referred to as working memory)
• Regulates emotional responses, motivation,
  executive functions, working memory
• Responsible for teaching a person to learn from
  consequences

• Vulnerable to injury since they sit just inside
  the front of the skull near a rough bony area
• Have extensive connections with many brain
  regions, especially with the parietal lobe and
  the limbic system (emotions).
• Includes the motor strip
• Sends signals to the muscles of the body, telling
  them what to do

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Frontal Lobes
Motor Strip
Prefrontal Cortex
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Frontal Lobe Injury

• Injury damages an individual's ability to . . .
• Synthesize signals from the environment
• Assign priorities
• Make decisions
• Initiate actions
• Attend to tasks
• Control emotions
• Behave and interact socially
• Make plans

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Frontal Lobe Injury in Children

• Prefrontal lobe injuries in young children
  sometimes go unnoticed
• Parents and teachers typically function as their
  frontal lobesthey organize, plan, and direct
  their childrens lives.
• As the child gets older and enters early
  adolescence, they are expected to be more
  independent and learn to manage themselves over
  time.
• In the child with a brain injury, the capability
  for more independent frontal lobe functioning has
  been diminished.

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Parietal Lobe
Sensory Strip

• Situated behind the frontal lobes
• Includes the primary sensory cortex which is
  posterior to the motor strip.
• The first part of the brain to consciously
  register physical sensations.
• Regulates responses to touch, heat, cold, pain,
  and body awareness

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Parietal Lobe Injury

• When one side of the lobe is injured, a person
  may not recognize that anything is wrong with
  movement on the other side of the body.
• Even more complex functions like attention can be
  affected by damage to the parietal lobes.

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Occipital Lobe

• Located in the lower back part of the brain
• The primary visual center of the brain
• Involves the visual cortex
• Connected to the eyes by optic nerves
• Optic nerves carrying signals meet at a
  "crossing" called the optic chiasm
• The left optic track carries signals from the
  rightside field of vision, and the right optic
  track takes signals from the left so that both
  sides of the brain "see" the same thing.
• Most of what a person "sees" derives its meaning
  from prior learning and symbolic representations.

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Temporal Lobes

• Rest on both sides of the brain
• The centers for language hearing
• Brocas Area
• located in the lower portion of the motor cortex
  in the left frontaltemporal lobe
• Controls muscles of the face and mouth and
  enables the production of speech
• Wernickes Area
• located left temporalparietal lobe
• Governs a persons understanding of speech
• With their connections to the hippocampus, the
  temporal lobes help in the longterm storage of
  permanent memories.

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Temporal Lobes
Brocas Area
Wernickes Area